A fully validated method for the determination of lacosamide in human plasma using gas chromatography with mass spectrometry: application for therapeutic drug monitoring

Development of a UPLC-MS/MS method for the determination of lacosamide and its metabolite and its application to drug-drug interaction

Lacosamide, a third-generation novel antiepileptic drug, was first approved in 2008 as an adjunct to partial seizures. In 2014, the U.S. Food and Drug Administration (FDA) approved it as a single agent for partial seizures. Since epilepsy is a chronic condition, most patients need long-term antiepileptic medicinal products, so it is even more important to consider the drug-drug interactions (DDIs). For the purpose of this experiment, an ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay with accuracy and simplicity was optimized and fully validated for the simultaneous quantitative determination of lacosamide and O-Desmethyl-lacosamide (ODL), and DDIs between lacosamide and nisoldipine in vivo and in vitro was researched. The protein was precipitated with acetonitrile, the analytes were eluted with acetonitrile and a 0.1% formic acid solution in a gradient program, and lacosamide, ODL, and lamotrigine (Internal Standard, IS) were successfully separated by chromatography. The findings of the biological analysis revealed that the lower limit of quantification (LLOQ) for lacosamide in samples was 2 ng/mL and the linearity ranged from 2 to 10000 ng/mL. The LLOQ for ODL was 1 ng/mL, while the linearity range for this substance was 1-1,000 ng/mL. In rat liver microsomes (RLM), the LLOQ of ODL was 80 ng/mL and the linear range was 80-40000 ng/mL. The selectivity, stability, matrix effect and recovery rate were all satisfied with the need of quantitative analysis of samples. Then, the UPLC-MS/MS assay was employed successfully on the interactions of lacosamide and nisoldipine in vivo and in vitro. The half-maximal inhibitory concentration (IC50) was 3.412 μM in RLM, where nisoldipine inhibited the metabolism of lacosamide with a mixture of inhibition mechanism. In rat pharmacokinetic experiments, it was found that nisoldipine could significantly change the pharmacokinetic characteristics of lacosamide, including AUC(0-t), AUC(0-∞), Tmax, CLz/F and Cmax, but had no significant effect on ODL. In summary, the UPLC-MS/MS method could accurately and sensitively quantify lacosamide and ODL, and could be used for the interaction between nisoldipine and lacosamide in vivo and in vitro.

Is Therapeutic Drug Monitoring of Lacosamide Needed in Patients with Seizures and Epilepsy?

Lacosamide is an antiepileptic drug (AED) that has linear pharmacokinetics, predictable blood concentrations, and few drug interactions, setting it apart from other AEDs that require vigorous therapeutic drug monitoring (TDM) such as phenytoin and carbamazepine. However, there have been reports of altered lacosamide pharmacokinetics in some populations. The purpose of this review is to determine whether lacosamide pharmacokinetics are altered in certain patient populations, suggesting the need for TDM. A literature search of Medline, Scopus, Embase, and Cochrane trials was conducted on January 3, 2019 (and then updated on September 2, 2019) to search for articles relevant to the TDM or pharmacokinetics of lacosamide. A total of 56 relevant articles were found and included in this review. Dose of lacosamide is linearly correlated with plasma concentrations and efficacy. However, currently there is no well-established reference range. Overall, the recommended reference ranges varied from 2.2 to 20 mg/L. Lacosamide has very few clinically relevant drug-drug interactions; however, there seems to be a significant drug interaction between lacosamide and enzyme-inducer AEDs. Based on available literature, it appears that lacosamide pharmacokinetics may be altered in severe renal dysfunction, in patients on dialysis and with extremes of age. More evidence is currently needed on lacosamide pharmacokinetics in pregnancy and critical illness. While it is not practical to utilize TDM for all patients, TDM may be useful in patients taking enzyme-inducer AEDs, in patients with decreased renal function or on dialysis, and older adults.

New Methods Used in Pharmacokinetics and Therapeutic Monitoring of the First and Newer Generations of Antiepileptic Drugs (AEDs)

The review presents data from the last few years on bioanalytical methods used in therapeutic drug monitoring (TDM) of the 1st-3rd generation and the newest antiepileptic drug (AEDs) cenobamate in patients with various forms of seizures. Chemical classification, structure, mechanism of action, pharmacokinetic data and therapeutic ranges for total and free fractions and interactions were collected. The primary data on bioanalytical methods for AEDs determination included biological matrices, sample preparation, dried blood spot (DBS) analysis, column resolution, detection method, validation parameters, and clinical utility. In conclusion, the most frequently described method used in AED analysis is the LC-based technique (HPLC, UHPLC, USLC) combined with highly sensitive mass detection or fluorescence detection. However, less sensitive UV is also used. Capillary electrophoresis and gas chromatography have been rarely applied. Besides the precipitation of proteins or LLE, an automatic SPE is often a sample preparation method. Derivatization was also indicated to improve sensitivity and automate the analysis. The usefulness of the methods for TDM was also highlighted.

Selective quantification of lacosamide in human plasma using UPLC-MS/MS: Application to pharmacokinetic study in healthy subjects with different doses

A practical, sensitive, and robust UPLC-MS/MS method was developed and validated to quantify lacosamide in human plasma. A simple one-step protein precipitation was used to extract lacosamide and labeled lacosamide-13C, D3 as an internal standard (IS) from 150-μL plasma. The extracts were analyzed on an Eclipse Plus C18 column (50 × 2.1 mm, 1.8 μm) using 0.1% formic acid in water and methanol:acetonitrile (50:50, v/v) under gradient conditions. The extracts were quantified on LCMS-8040 using electrospray ionization source operated in positive ionization and multiple reaction monitoring modes. The method showed good linearity from 0.02 to 20 μg/mL, which was adequate to cover lacosamide concentration assayed in formulations with different strengths. The bioanalytical assay was fully validated as per current regulatory guidelines. The intra-batch and inter-batch precision values of lacosamide were less than 4.6%. Lacosamide was found to be stable at different storage conditions. The extraction recoveries and IS-normalized matrix factors for lacosamide ranged from 97.17 to 99.68% and from 0.973 to 1.012, respectively. The validated method was successfully applied to a pharmacokinetic study with three lacosamide formulations (50, 100, and 200 mg) in 36 healthy subjects. The assay reliability was determined by reanalysis of 81 subject samples.

Α Simple Method for the Determination of Lacosamide in Blood by GC-MS

Lacosamide is a functionalized amino acid with antiepileptic function. Therapeutic drug monitoring (TDM) in patients for lacosamide is critical as it allows clinicians to control epileptic seizures. A single liquid-liquid extraction step was applied for the extraction of lacosamide from whole blood samples which were thereafter analyzed by GC-MS. Optimum extraction conditions were selected on the basis of experiments with various solvents at different pHs, indicating ethyl acetate at pH 12 as the most efficient parameters for the extraction of lacosamide. Method exhibited linearity from 2 to 100 μg/mL with R²  = 0.998. Accuracy and precision were evaluated at three concentrations and found to be within acceptable limits. LOD and LOQ were determined at 0.1 and 0.5 μg/mL, respectively. Lacosamide was found to be stable at storage conditions. The developed method was applied successfully in clinical samples and postmortem blood sample from an overdose case.

Highly sensitive UHPLC-DAD method for simultaneous determination of two synergistically acting antiepileptic drugs; levetiracetam and lacosamide: Application to pharmaceutical tablets and human urine

A simple and highly sensitive ultra-high-performance liquid chromatographic-diode array (UHPLC-DAD) detection method was developed and validated for the simultaneous estimation of levetiracetam (LEV) and lacosamide (LAC). It was clinically proven that the combination of LEV and LAC exhibits a synergistic effect against refractory seizures in mice, which was the motivation for the analysis of this binary mixture both in bulk and in human urine samples. The binary mixture was resolved on a Hypersil BDS C₁₈ analytical column, utilizing a mobile phase of 0.050 mol L^-1 phosphate buffer (pH 5.60), methanol and acetonitrile in the ratio (80:10:10 v/v/v) using catechol as an internal standard. The mobile phase was pumped at a flow rate of 1.2 mL min^-1 with diode array detection at 205 nm for both drugs and 270 nm for IS. Calibration curves were linear with correlation coefficient >0.9990 over the studied concentration range of 0.1-70.0 μg mL^-1 for both drugs. The developed method was reproducible with low relative standard deviation values for intra- and inter-day precision (<2.0%). Both drugs were determined in bulk, pharmaceutical formulations and human urine samples without any interference from complex matrices.

Green gas chromatographic stability-indicating method for the determination of Lacosamide in tablets. Application to in-vivo human urine profiling

A direct, eco-friendly, stability-indicating GC method was developed for the determination of Lacosamide (LCM) in tablet dosage forms in presence of its degradation products as well as in human urine in presence of the co-administered drug Zonisamide (ZON). The assay method in tablets was validated according to the ICH guidelines, while the method for determination of LCM in urine was validated according to FDA; Bioanalytical Method Validation guidance. Linear response (r = 0.9998) was observed over the range of 20-280 μg/mL of LCM, with detection and quantitation limits of 5.871 and 19.57 μg/mL, respectively for the tablet assay method. While (r = 0.9999) was observed over the range of 0.5-20 μg/mL of LCM, with detection and quantitation limits of 67 and 233 ng mL^-1, respectively for the urine analysis method. Under various stress conditions, the investigation of LCM forced degradation behaviour was carried out. Furthermore, monitoring of the drug in urine followed by construction of its urine profile was done after the administration of 50 mg tablet of LCM to three healthy volunteers so as to prove the ability of the method to be applied in assaying LCM in human urine. The method showed also successful separation of LCM and the co-administered drug ZON in urine. Finally, the greenness of the method was assessed using National Environmental Methods Index label and Eco scale methods.

An Updated Overview on Therapeutic Drug Monitoring of Recent Antiepileptic Drugs

Given the distinctive characteristics of both epilepsy and antiepileptic drugs (AEDs), therapeutic drug monitoring (TDM) can make a significant contribution to the field of epilepsy. The measurement and interpretation of serum drug concentrations can be of benefit in the treatment of uncontrollable seizures and in cases of clinical toxicity; it can aid in the individualization of therapy and in adjusting for variable or nonlinear pharmacokinetics; and can be useful in special populations such as pregnancy. This review examines the potential for TDM of newer AEDs such as eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, perampanel, pregabalin, rufinamide, retigabine, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. We describe the relationships between serum drug concentration, clinical effect, and adverse drug reactions for each AED as well as the different analytical methods used for serum drug quantification. We discuss retrospective studies and prospective data on the serum drug concentration-efficacy of these drugs and present the pharmacokinetic parameters, oral bioavailability, reference concentration range, and active metabolites of newer AEDs. Limited data are available for recent AEDs, and we discuss the connection between drug concentrations in terms of clinical efficacy and nonresponse. Although we do not propose routine TDM, serum drug measurement can play a beneficial role in patient management and treatment individualization. Standardized studies designed to assess, in particular, concentration-efficacy-toxicity relationships for recent AEDs are urgently required.